Previous histological, histochemical and ultrastructural research has established that the deer antler may be a significant model for studies of chondrogenesis and osteogenesis. Further clarification, however, is required. Current efforts will be directed toward the following: 1. a further clarification of the ultrastructural characteristics by selected cytochemical and enzyme techniques. 2. an ultrastructural characterization of the osseous replacement of cartilage. 3. a characterization of the numerous "chondroclasts" which extensively remodel the mineralized cartilage. 4. a cytochemical and ultrastructural comparison of perivascular cells in somatic metaphyses with perivascular spaces in remodeling antler cartilage. 5. initiate scanning electron microscopic studies of developing, maturing and mineralizing antler cartilage.